Actuator device

ABSTRACT

An actuator device includes a support part, a first movable part, and a second movable part. The second movable part includes a pair of first connection portions positioned on both sides of the first movable part on a first axis and connected to a pair of first connecting parts, and a pair of second connection portions positioned on both sides of the first movable part on a second axis and connected to a pair of second connecting parts. An outer edge of each of the pair of the first connection portions includes a first linear portion that extends along a second axis direction. An outer edge of each of the pair of the second connection portions includes a second linear portion that extends along a first axis direction.

TECHNICAL FIELD

An aspect of the disclosure relates to an actuator device formed of, forexample, a Micro Electro Mechanical Systems (MEMS) device.

BACKGROUND ART

An actuator device is known as a MEMS device. The actuator deviceincludes a support part, a first movable part, a frame-shaped secondmovable part that surrounds the first movable part, a pair of firstconnecting parts that connects the first movable part to the secondmovable part on a first axis, and a pair of second connecting parts thatconnects the second movable part to the support part on a second axisorthogonal to the first axis. In such an actuator device, the firstmovable part is made to swing around the first axis and the secondmovable part is made to swing around the second axis together with thefirst movable part (see, for example, Patent Literature 1).

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Unexamined Patent Publication No.    2014-41234

SUMMARY OF INVENTION Technical Problem

It is desired in the above-mentioned actuator device that the resonantfrequency of the second movable part around the second axis is high tosuppress the vibration of the second movable part caused by anunintended external force. On the other hand, when the first movablepart swings around the first axis, the second movable part may bedeformed to the side opposite to the first movable part around the firstaxis by a reaction against it. In this case, there is a concern that thesecond connecting parts need to be largely deformed to make the firstmovable part swing by a specified amount. Further, there is also aconcern that stress may be generated at an unintended part. For thisreason, it is preferable that the deformation of the second movable partaround the first axis is suppressed.

An object of an aspect of the disclosure is to provide an actuatordevice in which a first movable part swings around a first axis and asecond movable part surrounding the first movable part swings around asecond axis and that can achieve both the ensuring of the resonantfrequency of the second movable part around the second axis and thesuppression of the deformation of the second movable part around thefirst axis.

Solution to Problem

An actuator device according to an aspect of the disclosure includes asupport part, a first movable part, a frame-shaped second movable partthat is arranged so as to surround the first movable part, a pair offirst connecting parts that is arranged on both sides of the firstmovable part in a first axis direction parallel to a first axis andconnects the first movable part to the second movable part so that thefirst movable part can swing around the first axis, and a pair of secondconnecting parts that is arranged on both sides of the second movablepart in the first axis direction parallel to a second axis orthogonal tothe first axis and connects the second movable part to the support partso that the second movable part can swing around the second axis. Thesecond movable part includes a pair of first connection portions that ispositioned on both sides of the first movable part on the first axis andis connected to the pair of first connecting parts, and a pair of secondconnection portions that is positioned on both sides of the firstmovable part on the second axis and is connected to the pair of secondconnecting parts. Each of the pair of second connection portionsincludes a portion having a width larger than the width of a portion ofthe second movable part other than the pair of first connection portionsand the pair of second connection portions when viewed in a directionorthogonal to the first and second axes. An inner edge of each of thepair of second connection portions, when viewed in the directionorthogonal to the first and second axes, includes a depression portionrecessed in a second axis direction, and an outer edge of each of thepair of second connection portions, when viewed in the directionorthogonal to the first and second axes, includes a protrusion portionprotruding in the second axis direction.

In the actuator device, each of the pair of second connection portionspositioned on both sides of the first movable part on the second axisincludes a portion having a width larger than the width of a portion ofthe second movable part other than the pair of first connection portionsand the pair of second connection portions. Accordingly, while anincrease in the moment of inertia of the second movable part about thesecond axis is suppressed, the moment of inertia of the second movablepart about the first axis can be increased. As a result, both theensuring of the resonant frequency of the second movable part around thesecond axis and the suppression of the deformation of the second movablepart around the first axis can be achieved. Further, the inner edge ofeach of the second connection portions, when viewed in the directionorthogonal to the first and second axes, includes the depression portionrecessed in the second axis direction. Accordingly, the size of thesecond movable part can be reduced in the second axis direction, so thatan increase in the moment of inertia of the second movable part aboutthe second axis can be further suppressed. Furthermore, the outer edgeof each of the second connection portions, when viewed in the directionorthogonal to the first and second axes, includes the protrusion portionprotruding in the second axis direction. Accordingly, the moment ofinertia of the second movable part about the first axis can be furtherincreased. Moreover, since each of the second connection portions ispositioned on the second axis, an increase in the moment of inertia ofthe second movable part about the second axis can be still furthersuppressed. Therefore, according to this actuator device, both theensuring of the resonant frequency of the second movable part around thesecond axis and the suppression of the deformation of the second movablepart around the first axis can be achieved in the actuator device inwhich the first movable part swings around the first axis and the secondmovable part surrounding the first movable part swings around the secondaxis.

In the actuator device according to the aspect of the disclosure, thesecond movable part may further include a pair of first linear portionsthat is positioned on both sides of one of the pair of second connectionportions in the first axis direction and is connected to one of the pairof second connection portions, and a pair of second linear portions thatis positioned on both sides of the other of the pair of secondconnection portions in the first axis direction and is connected to theother of the pair of second connection portions, and each of the pair offirst linear portions and each of the pair of second linear portions mayextend in the first axis direction. In this case, while an increase inthe moment of inertia of the second movable part about the second axisis effectively suppressed, the moment of inertia of the second movablepart about the first axis can be effectively increased.

In the actuator device according to the aspect of the disclosure, thesecond movable part may further include a pair of third linear portionsthat is positioned on sides opposite to one of the pair of secondconnection portions with respect to the pair of first linear portionsand is connected to the pair of first linear portions, and a pair offourth linear portions that is positioned on sides opposite to the otherof the pair of second connection portions with respect to the pair ofsecond linear portions and is connected to the pair of second linearportions. When viewed in a direction orthogonal to the first and secondaxes, one of the pair of third linear portions may extend in a directioninclined with respect to the first and second axes, the other of thepair of third linear portions may extend symmetrically to one of thepair of third linear portions with respect to the second axis, one ofthe pair of fourth linear portions may extend symmetrically to one ofthe pair of third linear portions with respect to the first axis, andthe other of the pair of fourth linear portions may extend symmetricallyto one of the pair of fourth linear portions with respect to the secondaxis. In this case, while an increase in the moment of inertia of thesecond movable part about the second axis is more effectivelysuppressed, the moment of inertia of the second movable part about thefirst axis can be more effectively increased.

In the actuator device according to the aspect of the disclosure, thesecond movable part may further include a fifth linear portion that isconnected to one of the pair of first connection portions and one of thepair of second connection portions, a sixth linear portion that isconnected to one of the pair of first connection portions and the otherof the pair of second connection portions, a seventh linear portion thatis connected to the other of the pair of first connection portions andone of the pair of second connection portions, and an eighth linearportion that is connected to the other of the pair of first connectionportions and the other of the pair of second connection portions. Whenviewed in the direction orthogonal to the first and second axes, thefifth linear portion may extend in a direction inclined with respect tothe first and second axes, the sixth linear portion may extendsymmetrically to the fifth linear portion with respect to the firstaxis, the seventh linear portion may extend symmetrically to the fifthlinear portion with respect to the second axis, and the eighth linearportion may extend symmetrically to the sixth linear portion withrespect to the second axis. In this case, while an increase in themoment of inertia of the second movable part about the second axis iseffectively suppressed, the moment of inertia of the second movable partabout the first axis can be effectively increased.

In the actuator device according to the aspect of the disclosure, thedepression portion and the protrusion portion may be positioned on thesecond axis when viewed in the direction orthogonal to the first andsecond axes. In this case, while an increase in the moment of inertia ofthe second movable part about the second axis is still more effectivelysuppressed, the moment of inertia of the second movable part about thefirst axis can be still more effectively increased.

The actuator device according to the aspect of the disclosure mayfurther include a spiral coil that is provided to the second movablepart so as to surround the first movable part, and a magnetic fieldgenerator that generates a magnetic field to act on the coil. In thiscase, both the ensuring of the resonant frequency of the second movablepart around the second axis and the suppression of the deformation ofthe second movable part around the first axis can be achieved while anarrangement space of the coil is ensured in the second movable part.

In the actuator device according to the aspect of the disclosure, thecoil may be arranged at a position that is closer to the outer edge thanthe inner edge of each of the pair of second connection portions on thesecond axis when viewed in the direction orthogonal to the first andsecond axes. In this case, the moment of inertia of the second movablepart about the first axis can be still more effectively increased.

In the actuator device according to the aspect of the disclosure, thecoil may include a portion that extends in a direction orthogonal to themagnetic field. In this case, Lorentz force, which is generated by aninteraction between current flowing through the coil and a magneticfield, can be increased.

In the actuator device according to the aspect of the disclosure, thecoil may be made of a metal material of which the density is higher thanthe density of a material of the second movable part, and may beembedded in the second movable part. In this case, the moment of inertiaof the second movable part about the first axis can be still moreeffectively increased.

In the actuator device according to the aspect of the disclosure, eachof the pair of second connection portions may include a portion having awidth larger than the width of each of the pair of first connectionportions. In this case, while an increase in the moment of inertia ofthe second movable part about the second axis is still more effectivelysuppressed, the moment of inertia of the second movable part about thefirst axis can be still more effectively increased.

In the actuator device according to the aspect of the disclosure, thedepression portion may be provided over a region of each of the pair ofsecond connection portions facing the first movable part when viewed inthe direction orthogonal to the first and second axes. In this case, themoment of inertia of the second movable part about the first axis can bestill more effectively increased.

In the actuator device according to the aspect of the disclosure, eachof the pair of second connecting parts may extend meanderingly whenviewed in the direction orthogonal to the first and second axes. In thiscase, the strength of each second connecting part can be improved, andthe adjustment of the spring constant of each second connecting part canbe facilitated. Further, an increase in the size of the device in thesecond axis direction can be suppressed.

Advantageous Effects of Invention

According to an aspect of the disclosure, both the ensuring of theresonant frequency of a second movable part around a second axis and thesuppression of the deformation of the second movable part around a firstaxis can be achieved in an actuator device in which a first movable partswings around the first axis and the second movable part surrounding thefirst movable part swings around the second axis.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view of an actuator device according to an embodiment.

FIG. 2 is a cross-sectional view taken along line II-II illustrated inFIG. 1 .

FIG. 3 is an enlarged plan view of a part of FIG. 1 .

FIG. 4 is a plan view illustrating a modification.

DESCRIPTION OF EMBODIMENTS

An embodiment of the disclosure will be described in detail below withreference to the drawings. in the following description, the same orcorresponding elements are denoted by the same reference numerals andthe repeated description thereof will be omitted.

As illustrated in FIG. 1 , an actuator device 1 includes a support part2, a first movable part 3, a second movable part 4, a pair of firsttorsion bars (first connecting part) 5 and 6, a pair of second torsionbars (second connecting part) 7 and 8, and a magnetic field generator 9.The support part 2, the first movable part 3, the second movable part 4,the pair of first torsion bars 5 and 6, and the pair of second torsionbars 7 and 8 are integrally formed by, for example, a Silicon onInsulator (SOI) substrate. That is, the actuator device 1 is formed of aMEMS device. In the actuator device 1, the first movable part 3 providedwith a mirror surface 10 is made to swing around each of an X axis(first axis) and a Y axis (second axis orthogonal to the first axis)orthogonal to each other. The actuator device 1 is used for, forexample, an optical switch for optical communication, an opticalscanner, and the like. The actuator device 1 is manufactured using aMEMS technology (patterning, etching, and the like).

The magnetic field generator 9 is formed of permanent magnets and thelike arranged in a Halbach array. The magnetic field generator 9generates, for example, a magnetic field in a direction D inclined withrespect to each of the X axis and the Y axis by an angle of 45° in planview (when viewed in a direction orthogonal to the X axis and the Yaxis), and causes the magnetic field to act on a coil 14 to be describedlater. The direction D of the magnetic field generated by the magneticfield generator 9 may be inclined with respect to the X axis and the Yaxis by an angle other than 45° in plan view.

The support part 2 has, for example, a rectangular outer shape in planview and is formed in the shape of a frame. The support part 2 isarranged on one side of the magnetic field generator 9 in the directionorthogonal to the X axis and the Y axis. The first movable part 3 isarranged inside the support part 2 in a state where the first movablepart 3 is spaced from the magnetic field generator 9. The first movablepart 3 includes a body portion 3 a, a ring shape portion 3 b, and a pairof connecting portions 3 c.

The body portion 3 a has a circular shape in plan view, but may beformed in any shape, such as an elliptical shape, a rectangular shape,or a rhombic shape. The center P of the body portion 3 a in plan viewcoincides with the intersection of the X axis and the Y axis. The mirrorsurface 10 is provided on the surface of the body portion 3 a oppositeto the magnetic field generator by a metal film made of, for example,aluminum. The mirror surface 10 is provided over the entire surface ofthe body portion, but may be provided on only a part of the surface ofthe body portion. The ring shape portion 3 b is formed in an ring shapeso as to surround the body portion 3 a in plan view. The ring shapeportion 3 b has an octagonal outer shape in plan view, but may have anarbitrary outer shape, such as a circular shape, an elliptical shape, arectangular shape, or a rhombic shape. The pair of connecting portions 3c is arranged on both sides of the body portion 3 a on the Y axis, andconnects the body portion 3 a to the ring shape portion 3 b.

The second movable part 4 is formed in the shape of a frame, and isarranged inside the support part 2 so as to surround the first movablepart 3 in a state where the second movable part 4 is spaced from themagnetic field generator 9. The detailed configuration of the secondmovable part 4 will be described later.

The first torsion bars 5 and 6 are arranged on both sides of the firstmovable part 3 on the X axis. The first torsion bars 5 and 6 connect thefirst movable part 3 (ring shape portion 3 b) to the second movable part4 on the X axis so that the first movable part 3 can swing around the Xaxis (around the X axis as a center line). Each of the first torsionbars 5 and 6 extends linearly along the X axis. In this embodiment, fora reduction in stress acting on the first torsion bars 5 and 6, thewidth of an end portion of each of the first torsion bars 5 and 6 closeto the first movable part 3 increases as approaching the first movablepart 3, and the width of an end portion of each of the first torsionbars 5 and 6 close to the second movable part 4 increases as approachingthe second movable part 4.

The second torsion bars 7 and 8 are arranged on both sides of the secondmovable part 4 on the Y axis. The second torsion bars 7 and 8 connectthe second movable part 4 to the support part 2 on the Y axis so thatthe second movable part 4 can swing around the Y axis (around the Y axisas a center line). Each of the second torsion bars 7 and 8 extendsmeanderingly in plan view. Each of the second torsion bars 7 and 8includes a plurality of linear portions 11 and a plurality of foldedportions 12. The linear portions 11 extend in a Y-axis direction (secondaxis direction) parallel to the Y axis, and are arranged side by side inan X-axis direction (first axis direction) parallel to the X axis. Thefolded portions 12 alternately connect both ends of the adjacent linearportions 11.

The actuator device 1 further includes a pair of coils 14 and 15, aplurality of wirings 21, 22, 23, and 24, and a plurality of electrodepads 25, 26, 27, and 28. Each of the coils 14 and 15 is provided in thesecond movable part 4 so as to surround the first movable part 3, andhas a spiral shape in plan view. Each of the coils 14 and 15 is woundaround the first movable part 3 a plurality of times. The pair of coils14 and 15 is alternately arranged side by side in the width direction ofthe second movable part 4 in plan view. A region R where the coils 14and 15 are arranged is illustrated in FIG. 1 by hatching. The detailshapes and arrangement of the coils 14 and 15 in plan view will bedescribed later.

FIG. 2 is a cross-sectional view taken along line II-II illustrated inFIG. 1 . As illustrated in FIG. 2 , the second movable part 4 isprovided with groove portions 31 having shapes corresponding to therespective coils 14 and 15. An insulating layer 32 is provided on theinner surfaces of the groove portions 31, and an insulating layer 33 isprovided on the insulating layer 32. Each of the coils 14 and 15 isarranged in the groove portion 31 via the insulating layers 32 and 33.Each of the coils 14 and 15 is a damascene wiring embedded in the secondmovable part 4. An insulating layer 34 is provided so as to cover thecoils 14 and 15 and the insulating layer 33. An insulating layer 35 isprovided on the insulating layer 34. Each of the insulating layers 32 to35 is made of, for example, silicon oxide, silicon nitride, siliconoxynitride, or the like. Each of the insulating layers 32 to 35 isintegrally formed so as to cover the surfaces (surfaces opposite to themagnetic field generator 9) of the support part 2, the first movablepart 3, the second movable part 4, the first torsion bars 5 and 6, andthe second torsion bars 7 and 8.

Each of the coils 14 and 15 is made of a metal material of which thedensity is higher than the density of the material of the second movablepart 4. In this embodiment, the second movable part 4 is made of siliconand each of the coils 14 and 15 is made of copper. Each of the coils 14and 15 may be made of gold.

Each of the electrode pads 25 to 28 is provided on the support part 2,and is exposed to the outside from the insulating layer 35. The wiring21 is electrically connected to one end of the coil 14 and the electrodepad 25. The wiring 21 extends to the electrode pad 25 from one end ofthe coil 14 through the second torsion bar 7. The wiring 22 iselectrically connected to the other end of the coil 14 and the electrodepad 26. The wiring 22 extends to the electrode pad 26 from the other endof the coil 14 through the second torsion bar 8. Each of the wirings 21and 22 may be a damascene wiring that is formed as with, for example,each of the coils 14 and 15, and may be a wiring arranged on the surfaceof the support part 2 or the like.

The wiring 23 is electrically connected to one end of the coil 15 andthe electrode pad 27. The wiring 23 extends to the electrode pad 27 fromone end of the coil 15 through the second torsion bar 7. The wiring 24is electrically connected to the other end of the coil 15 and theelectrode pad 28. The wiring 24 extends to the electrode pad 28 from theother end of the coil 15 through the second torsion bar 8. Each of thewirings 23 and 24 may be a damascene wiring that is formed as with, forexample, each of the coils 14 and 15, and may be a wiring arranged onthe surface of the support part 2 or the like.

In the actuator device 1 having the above-mentioned configuration, whena drive signal for a linear operation is input to the coil 14 throughthe electrode pads 25 and 26 and the wirings 21 and 22, Lorentz forceacts on the coil 14 due to an interaction between the drive signal andthe magnetic field generated by the magnetic field generator 9. Themirror surface 10 (first movable part 3) can be linearly operated aroundthe Y axis together with the second movable part 4 using a balancebetween the Lorentz force and the elastic forces of the second torsionbars 7 and 8.

On the other hand, when a drive signal for a resonant operation is inputto the coil 15 through the electrode pads 27 and 28 and the wirings 23and 24, Lorentz force acts on the coil 15 due to an interaction betweenthe drive signal and the magnetic field generated by the magnetic fieldgenerator 9. The mirror surface 10 (first movable part 3) can beoperated to resonate around the X axis using the resonance of the firstmovable part 3 at a resonant frequency in addition to the Lorentz force.Specifically, when a drive signal having a frequency equal to theresonant frequency of the first movable part 3 around the X axis isinput to the coil 15, the second movable part 4 slightly vibrates aroundthe X axis at this frequency. This vibration is transmitted to the firstmovable part 3 through the first torsion bars 5 and 6, so that the firstmovable part 3 can swing around the X axis at this frequency.

Subsequently, the detailed configuration of the second movable part 4will be described. As illustrated in FIG. 1 , the second movable part 4includes a pair of first connection portions 41A and 41B, a pair ofsecond connection portions 42A and 42B, a pair of first linear portions43A and 43B, a pair of second linear portions 44A and 44B, a pair ofthird linear portions 45A and 45B, and a pair of fourth linear portions46A and 46B. The second movable part 4 has a shape symmetrical withrespect to each of the X axis and the Y axis in plan view. In thefollowing description, symmetry with respect to the X axis or the Y axismeans symmetry in plan view.

The first connection portions 41A and 41B are positioned on both sidesof the first movable part 3 on the X axis. Each of the first connectionportions 41A and 41B includes a portion facing the first movable part 3in the X-axis direction in plan view. Each of the first connectionportions 41A and 41B extends in the Y-axis direction. The firstconnection portions 41A and 41B are connected to the first torsion bars5 and 6. That is, the first torsion bars 5 and 6 are connected to thesecond movable part 4 at the first connection portions 41A and 41B.

The second connection portions 42A and 42B are positioned on both sidesof the first movable part 3 on the Y axis. Each of the second connectionportions 42A and 42B includes a portion facing the first movable part 3in the Y-axis direction in plan view. Each of the second connectionportions 42A and 42B extends in the X-axis direction. The secondconnection portions 42A and 42B are connected to the second torsion bars7 and 8. That is, the second torsion bars 7 and 8 are connected to thesecond movable part 4 at the second connection portions 42A and 42B.

The first linear portions 43A and 43B are positioned on both sides ofthe second connection portion 42A in the X-axis direction, and areconnected to the second connection portion 42A. Each of the first linearportions 43A and 43B extends in the X-axis direction. The first linearportions 43A and 43B are arranged symmetrically to each other withrespect to the Y axis. The second linear portions 44A and 44B arepositioned on both sides of the second connection portion 42B in theX-axis direction, and are connected to the second connection portion42B. Each of the second linear portions 44A and 44B extends in theX-axis direction. The second linear portions 44A and 44B are arrangedsymmetrically to each other with respect to the Y axis.

The third linear portions 45A and 45B are positioned on the sidesopposite to the second connection portion 42A with respect to the firstlinear portions 43A and 43B, and are connected to the first linearportions 43A and 43B and the first connection portions 41A and 41B. Thethird linear portion 45A extends in a direction inclined with respect toeach of the X axis and the Y axis by an angle of 45° in plan view. Thethird linear portion 45B extends symmetrically to the third linearportion 45A with respect to the Y axis. A direction in which the thirdlinear portion 45A extends may be inclined with respect to the X axisand the Y axis by an angle other than 45°.

The fourth linear portions 46A and 46B are positioned on the sidesopposite to the second connection portion 42B with respect to secondlinear portions 44A and 44B, and are connected to the second linearportions 44A and 44B and the first connection portions 41A and 41B. Thefourth linear portion 46A extends symmetrically to the third linearportion 45A with respect to the X axis. The fourth linear portion 46Bextends symmetrically to the fourth linear portion 46A with respect tothe Y axis, and extends symmetrically to the third linear portion 45Bwith respect to the X axis.

The configuration of the second connection portion 42A will be describedin more detail with reference to FIG. 3 . The second connection portion42A will be described below. However, the second connection portion 42Bis configured symmetrically to the second connection portion 42A withrespect to the X axis, and has the same configuration as the secondconnection portion 42A. An inner edge 51 of the second connectionportion 42A in plan view includes one depression portion 52 recessed inthe Y-axis direction. The depression portion 52 is recessed from theinner edge of each of the first linear portions 43A and 43B toward theside opposite to the first movable part 3. The depression portion 52 ispositioned on the Y axis in plan view. The depression portion 52 isprovided over a region of the second connection portion 42A facing thefirst movable part 3 in plan view. The inner edge 51 of the region wherethe depression portion 52 is formed is curved so as to go away from thefirst movable part 3 as approaching the Y axis. The inner edge 51 of aregion where the depression portion 52 is not formed extends in theX-axis direction. The curvature of the inner edge 51 is continuous at aboundary between the region where the depression portion 52 is formedand the region where the depression portion 52 is not formed.

An outer edge 53 of the second connection portion 42A in plan viewincludes one protrusion portion 54 protruding in the Y-axis direction.The protrusion portion 54 protrudes from the outer edge of each of thefirst linear portions 43A and 43B toward the side opposite to the firstmovable part 3. The protrusion portion 54 is positioned on the Y axis inplan view. The protrusion portion 54 is provided over a region of thesecond connection portion 42A facing the first movable part 3 in planview. The protrusion portion 54 does not have a shape corresponding tothe depression portion 52. That is, the outer edge 53 includes a portionformed not along the inner edge 51. The outer edge 53 of a region wherethe protrusion portion 54 is formed includes a linear portion 53 a and apair of curved portions 53 b. The linear portion 53 a extends in theX-axis direction, and crosses the Y axis in plan view. Each curvedportion 53 b has a curved shape so as to be recessed inward, and isconnected to the linear portion 53 a. The curvature of the outer edge 53is continuous at a boundary between the linear portion 53 a and eachcurved portion 53 b. The pair of curved portions 53 b is connected tothe outer edges of the first linear portions 43A and 43B so that thecurvature is continuous at the boundary.

The second connection portion 42A includes a portion (widened portion)having a width larger than the width of a portion of the second movablepart 4 other than the first connection portions 41A and 41B and thesecond connection portions 42A and 42B in plan view. In this embodiment,the widths of the respective linear portions 43A to 46B are equal toeach other. Accordingly, the width (maximum width) W1 of the portion ofthe second movable part 4 other than the first connection portions 41Aand 41B and the second connection portions 42A and 42B is the width ofeach of the linear portions 43A to 46B. The width of the secondconnection portion 42A is the minimum width W2 on the Y axis. Theminimum width W2 is larger than the width W1. Accordingly, the entiresecond connection portion 42A has a width larger than the width W1 inthis embodiment.

Further, the minimum width W2 of the second connection portion 42A islarger than the width (maximum width) W3 of each of the first connectionportions 41A and 41B. The width W3 of each of the first connectionportions 41A and 41B is larger than the above-mentioned width W1, butmay be equal to the width W1 or may be smaller than the width W1. Aboundary between the first connection portion 41A and the first torsionbar 5 is illustrated in FIG. 3 by a one-dot chain line B. The width of acertain portion of the second movable part 4 is a distance between theinner edge and the outer edge of this portion in plan view, that is, isthe width of this portion in a direction (width direction) orthogonal toa direction orthogonal to the X axis and the Y axis and a directionorthogonal to the extending direction of this portion. For example, thewidth of the first connection portion 41A is the width of the firstconnection portion 41A in the X-axis direction, and the width of thesecond connection portion 42A is the width of the second connectionportion 42A in the Y-axis direction.

Subsequently, the detail shapes and arrangement of the coils 14 and 15in plan view will be described. As illustrated in FIGS. 1 and 3 , eachof the coils 14 and 15 extends in the extending directions of the firstconnection portions 41A and 41B and the respective linear portions 43Ato 46B at the first connection portions 41A and 41B and the respectivelinear portions 43A to 46B. Each of the coils 14 and 15 provided at thethird and fourth linear portions 45B and 46A extends in a directionorthogonal to the magnetic field generated by the magnetic fieldgenerator 9. At the first connection portions 41A and 41B and therespective linear portions 43A to 46B, the outer edge of the region Rwhere the coils 14 and 15 are arranged extends along the outer edges ofthe first connection portions 41A and 41B and the respective linearportions 43A to 46B and the inner edge of the region R extends along theinner edges of the first connection portions 41A and 41B and therespective linear portions 43A to 46B.

As illustrated in FIG. 3 , the region R in the second connection portion42A includes a first portion 55, a pair of second portions 56, and apair of third portions 57. The first portion 55 extends in the X-axisdirection, and crosses the Y axis in plan view. The pair of secondportions 56 is positioned on both sides of the first portion 55 in theX-axis direction, and is connected to the first portion 55. One secondportion 56 extends in the direction inclined with respect to each of theX axis and the Y axis by an angle of 45°. The other second portion 56extends symmetrically to one second portion 56 with respect to the Yaxis. Each of the coils 14 and 15 provided in the other second portion56 extends in the direction orthogonal to the magnetic field generatedby the magnetic field generator 9. The first portion 55 is arranged at aposition closer to the outer edge 53 than the inner edge 51 of thesecond connection portion 42A. That is, a distance between the firstportion 55 and the inner edge 51 is longer than a distance between thefirst portion 55 and the outer edge 53. The pair of third portions 57 ispositioned on the sides opposite to the first portion 55 with respect tothe second portions 56, and is connected to the pair of second portions56 and the region R of the first linear portions 43A and 43B. Each thirdportion 57 extends in the X-axis direction. A direction where one secondportion 56 extends may be inclined with respect to the X axis and the Yaxis by an angle other than 45°.

As described above, in the actuator device 1, each of the pair of secondconnection portions 42A and 42B positioned on both sides of the firstmovable part 3 on the Y axis includes a portion having a width largerthan the width of a portion of the second movable part 4 other than thefirst connection portions 41A and 41B and the second connection portions42A and 42B. Accordingly, while an increase in the moment of inertia ofthe second movable part 4 about the Y axis is suppressed, the moment ofinertia of the second movable part 4 about the X axis can be increased.That is, the resonant frequency of the second movable part 4 around theY axis is larger as the moment of inertia of the second movable part 4about the Y axis is smaller. It is more difficult for the second movablepart 4 to be deformed around the X axis as the moment of inertia of thesecond movable part 4 about the X axis is larger. Accordingly, both theensuring of the resonant frequency of the second movable part 4 aroundthe Y axis and the suppression of the deformation of the second movablepart 4 around the X axis can be achieved in the actuator device 1.

Further, in the actuator device 1, the inner edge 51 of each of thesecond connection portions 42A and 42B in plan view includes thedepression portion 52 recessed in the Y-axis direction. Accordingly, thesize of the second movable part 4 can be reduced in the Y-axisdirection, so that an increase in the moment of inertia of the secondmovable part 4 about the Y axis can be further suppressed. Furthermore,the outer edge 53 of each of the second connection portions 42A and 42Bin plan view includes the protrusion portion 54 protruding in the Y-axisdirection. Accordingly, the moment of inertia of the second movable part4 about the X axis can be further increased. Moreover, since each of thesecond connection portions 42A and 42B is positioned on the Y axis, anincrease in the moment of inertia of the second movable part 4 about theY axis can be still further suppressed. Therefore, according to theactuator device 1, both the ensuring of the resonant frequency of thesecond movable part 4 around the Y axis and the suppression of thedeformation of the second movable part 4 around the X axis can beachieved in the actuator device 1 in which the first movable part 3swings around the X axis and the second movable part 4 surrounding thefirst movable part 3 swings around the Y axis. For example, according tothe actuator device 1, the moment of inertia of the second movable part4 about the X axis can be effectively increased in comparison with acase where the outer shape of the second movable part 4 in plan view isa substantially rhombic shape.

In the actuator device 1, the second movable part 4 further includes thefirst linear portions 43A and 43B and the second linear portions 44A and44B. Accordingly, while an increase in the moment of inertia of thesecond movable part 4 about the Y axis is effectively suppressed, themoment of inertia of the second movable part 4 about the X axis can beeffectively increased.

In the actuator device 1, the second movable part 4 further includes thethird linear portions 45A and 45B and the fourth linear portions 46A and46B. Accordingly, the length of a portion of the second movable part 4extending in the Y-axis direction can be shortened. As a result, whilean increase in the moment of inertia of the second movable part 4 aboutthe Y axis is more effectively suppressed, the moment of inertia of thesecond movable part 4 about the X axis can be more effectivelyincreased.

In the actuator device 1, the depression portions 52 and the protrusionportions 54 are positioned on the Y axis in plan view. Accordingly,while an increase in the moment of inertia of the second movable part 4about the Y axis is still more effectively suppressed, the moment ofinertia of the second movable part 4 about the X axis can be still moreeffectively increased.

The actuator device 1 includes the coils 14 and 15 and the magneticfield generator 9. Accordingly, both the ensuring of the resonantfrequency of the second movable part 4 around the Y axis and thesuppression of the deformation of the second movable part 4 around the Xaxis can be achieved while an arrangement space of the coils 14 and 15is ensured in the second movable part 4.

In the actuator device 1, each of the coils 14 and 15 is arranged at aposition that is closer to the outer edge 53 than the inner edge 51 ofeach of the second connection portions 42A and 42B. Accordingly, themoment of inertia of the second movable part 4 about the X axis can bestill more effectively increased.

In the actuator device 1, each of the coils 14 and 15 includes a portionextending in the direction orthogonal to the magnetic field.Accordingly, Lorentz force, which is generated by an interaction betweencurrent flowing through the coils 14 and 15 and a magnetic field, can beincreased.

In the actuator device 1, each of the coils 14 and 15 is made of a metalmaterial of which the density is higher than the density of the materialof the second movable part 4 and is embedded in the second movable part4. Accordingly, the moment of inertia of the second movable part 4 aboutthe X axis can be still more effectively increased.

In the actuator device 1, each of the second connection portions 42A and42B includes a portion having a width larger than the width of each ofthe first connection portions 41A and 41B. Accordingly, while anincrease in the moment of inertia of the second movable part 4 about theY axis is still more effectively suppressed, the moment of inertia ofthe second movable part 4 about the X axis can be still more effectivelyincreased.

In the actuator device 1, the depression portion 52 is provided over aregion of each of the second connection portions 42A and 42B facing thefirst movable part 3 in plan view. Accordingly, the moment of inertia ofthe second movable part 4 about the X axis can be still more effectivelyincreased. Further, a space where the first movable part 3 swings can besuitably ensured.

In the actuator device 1, each of the second torsion bars 7 and 8extends meanderingly in plan view. Accordingly, the strength of each ofthe second torsion bars 7 and 8 can be improved, and the adjustment ofthe spring constants of the second torsion bars 7 and 8 can befacilitated. Further, even though the length of the second movable part4 in the Y-axis direction is increased due to the protrusion portions54, an increase in the size of the device in the Y-axis direction can besuppressed.

One embodiment of the disclosure has been described above, but thedisclosure is not limited to the embodiment. The second movable part 4may be adapted as in a modification illustrated in, for example, FIG. 4. In this modification, the second movable part 4 includes a fifthlinear portion 61, a sixth linear portion 62, a seventh linear portion63, and an eighth linear portion 64. The fifth linear portion 61 isconnected to the first connection portion 41A and the second connectionportion 42A. The sixth linear portion 62 is connected to the firstconnection portion 41A and the second connection portion 42B. Theseventh linear portion 63 is connected to the first connection portion41B and the second connection portion 42A. The eighth linear portion 64is connected to the first connection portion 41B and the secondconnection portion 42B. The fifth linear portion 61 extends in adirection inclined with respect to the X axis and the Y axis in planview. The sixth linear portion 62 extends symmetrically to the fifthlinear portion 61 with respect to the X axis. The seventh linear portion63 extends symmetrically to the fifth linear portion 61 with respect tothe Y axis. The eighth linear portion 64 extends symmetrically to thesixth linear portion 62 with respect to the Y axis. The eighth linearportion 64 extends symmetrically to the seventh linear portion 63 withrespect to the X axis. Even in this modification, as in the embodiment,both the ensuring of the resonant frequency of the second movable part 4around the Y axis and the suppression of the deformation of the secondmovable part 4 around the X axis can be achieved. Further, since thesecond movable part 4 includes the linear portions 61 to 64, the momentof inertia of the second movable part 4 about the X axis can beeffectively increased while an increase in the moment of inertia of thesecond movable part 4 about the Y axis is effectively suppressed.

The first movable part 3 is driven by an electromagnetic force in theembodiment, but the first movable part 3 may be driven by apiezoelectric element. In this case, for example, the second movablepart 4 is provided with a first piezoelectric film that causes the firstmovable part 3 to swing around the X axis, instead of the coils 14 and15. The first piezoelectric film is arranged on, for example, the secondconnection portions 42A and 42B, the first linear portions 43A and 43B,and the second linear portions 44A and 44B. Further, each of the secondtorsion bars 7 and 8 is provided with a second piezoelectric film thatcauses the second movable part 4 to swing around the Y axis. Themagnetic field generator 9 will be omitted.

The first and second movable parts 3 and 4 are linearly operated aroundthe Y axis in the embodiment, but the first and second movable parts 3and 4 may be operated to resonate around the Y axis. The second movablepart 4 is provided with the pair of coils 14 and 15 in the embodiment,but the second movable part 4 may be provided with only one coil. Evenin this case, the first movable part can swing around the X axis and thesecond movable part 4 can swing around the Y axis by the input of adrive signal to the coil. Alternatively, the first movable part 3 may beprovided with one coil that causes the first movable part 3 to swingaround the X axis, and the second movable part 4 may be provided withone coil that causes the second movable part 4 to swing around the Yaxis. In the embodiment, the second movable part 4 may be provided withan electromotive force-monitoring coil for measuring an electromotiveforce and the support part 2 may be provided with a temperature sensorcoil for measuring a temperature. The respective coils 14 and 15 may bearranged on the second movable part 4 without being embedded in thesecond movable part 4.

The material and shape of each component are not limited to theabove-mentioned material and shape, and various materials and shapes canbe employed. The outer edge 53 of each of the second connection portions42A and 42B may include a plurality of protrusion portions protruding inthe Y-axis direction. For example, the outer edge 53 may include a pairof protrusion portions arranged symmetrically to each other with respectto the Y axis. In this case, the outer edge 53 between the twoprotrusion portions extends linearly in the X-axis direction, and thesecond torsion bars 7 and 8 may be connected to this linear portion. Inthis case, the protrusion portions are not positioned on the Y axis inplan view. Likewise, the inner edge 51 of each of the second connectionportions 42A and 42B may include a plurality of depression portionsrecessed in the Y-axis direction, and the depression portions may not bepositioned on the Y axis in plan view. The shape of each of thedepression portion 52 and the protrusion portion 54 in plan view may bean arbitrary shape, such as a rectangular shape, a semicircular shape,or a semi-elliptical shape. The protrusion portion 54 may be providedwith a slit or a depression portion.

Each of the second connection portions 42A and 42B has only to include aportion having a width larger than the width W1 of a portion of thesecond movable part 4 other than the first connection portions 41A and41B and the second connection portions 42A and 42B, and may include aportion having a width equal to the width W1 or a width smaller than thewidth W1. Each of the second connection portions 42A and 42B may notinclude a portion having a width larger than the width W3 of each of thefirst connection portions 41A and 41B.

The shape of the second movable part 4 is not limited to theabove-mentioned example. For example, the third linear portions 45A and45B and the fourth linear portions 46A and 46B may not be provided, andthe first linear portions 43A and 43B and the second linear portions 44Aand 44B may be directly connected to the first connection portions 41Aand 41B. Alternatively, the first linear portions 43A and 43B and thesecond linear portions 44A and 44B may not be provided, and third linearportions 45A and 45B and the fourth linear portions 46A and 46B may bedirectly connected to the second connection portions 42A and 42B. Thesecond movable part 4 may have a substantially circular shape, asubstantially elliptical shape, a substantially rectangular shape, orthe like in plan view. The ring shape portion 3 b may not be provided,and the first torsion bars 5 and 6 may be directly connected to the bodyportion 3 a. The first torsion bars 5 and 6 have only to be arranged onboth sides of the first movable part 3 in the X-axis direction, and mayconnect the first movable part 3 to the second movable part 4 atpositions other than the positions on the X axis. The second torsionbars 7 and 8 have only to be arranged on both sides of the secondmovable part 4 in the Y-axis direction, and may connect the secondmovable part 4 to the support part 2 at positions other than thepositions on the Y axis. The second torsion bars 7 and 8 may extendlinearly in plan view. The actuator device 1 may be a device to drive aportion other than the mirror surface 10. Each of the linear portions43A to 46B has only to extend in a certain direction, the inner edge ofat least one of the linear portions 43A to 46B in plan view may includea depression portion or a protrusion portion, and the outer edge of atleast one of the linear portions 43A to 46B in plan view may include adepression portion or a protrusion portion.

REFERENCE SIGNS LIST

-   -   1: actuator device, 2: support part, 3: first movable part, 4:        second movable part, 5, 6: first torsion bar (first connecting        part), 7, 8: second torsion bar (second connecting part), 9:        magnetic field generator, 14, 15: coil, 41A, 41B: first        connection portion, 42A, 42B: second connection portion, 43A,        43B: first linear portion, 44A, 44B: second linear portion, 45A,        45B: third linear portion, 46A, 46B: fourth linear portion, 51:        inner edge, 52: depression portion, 53: outer edge, 54:        protrusion portion.

1. An actuator device comprising: a support part; a first movable part;a second movable part formed in a frame shape and arranged so as tosurround the first movable part, wherein a coil is provided to thesecond movable part; a pair of first connecting parts arranged on bothsides of the first movable part in a first axis direction parallel to afirst axis and connecting the first movable part to the second movablepart so that the first movable part can swing around the first axis; anda pair of second connecting parts arranged on both sides of the secondmovable part in a second axis direction parallel to a second axisorthogonal to the first axis and connecting the second movable part tothe support part so that the second movable part can swing around thesecond axis, wherein the second movable part includes a pair of firstconnection portions positioned on both sides of the first movable parton the first axis and connected to the pair of first connecting parts,and a pair of second connection portions positioned on both sides of thefirst movable part on the second axis and connected to the pair ofsecond connecting parts, an outer edge of each of the pair of the firstconnection portions includes a first linear portion that extends alongthe second axis direction, an outer edge of each of the pair of thesecond connection portions includes a second linear portion that extendsalong the first axis direction, and a width of each of the pair of thesecond connection portions is larger than a width of each of the pair ofthe first connection portions when viewed in a direction orthogonal tothe first and second axes.
 2. The actuator device according to claim 1,wherein the second movable part further includes a pair of first linearportions positioned on both sides of one of the pair of secondconnection portions in the first axis direction and connected to the oneof the pair of second connection portions, and a pair of second linearportions positioned on both sides of the other of the pair of secondconnection portions in the first axis direction and connected to theother of the pair of second connection portions, and each of the pair offirst linear portions and each of the pair of second linear portionsextend in the first axis direction.
 3. The actuator device according toclaim 2, wherein the second movable part further includes a pair ofthird linear portions positioned on sides opposite to the one of thepair of second connection portions with respect to the pair of firstlinear portions and connected to the pair of first linear portions, anda pair of fourth linear portions positioned on sides opposite to theother of the pair of second connection portions with respect to the pairof second linear portions and connected to the pair of second linearportions, and when viewed in the direction orthogonal to the first andsecond axes, one of the pair of third linear portions extends in adirection inclined with respect to the first and second axes, the otherof the pair of third linear portions extends symmetrically to the one ofthe pair of third linear portions with respect to the second axis, oneof the pair of fourth linear portions extends symmetrically to the oneof the pair of third linear portions with respect to the first axis, andthe other of the pair of fourth linear portions extends symmetrically tothe one of the pair of fourth linear portions with respect to the secondaxis.
 4. The actuator device according to claim 1, wherein the secondmovable part further includes a fifth linear portion connected to one ofthe pair of first connection portions and one of the pair of secondconnection portions, a sixth linear portion connected to the one of thepair of first connection portions and the other of the pair of secondconnection portions, a seventh linear portion connected to the other ofthe pair of first connection portions and the one of the pair of secondconnection portions, and an eighth linear portion connected to the otherof the pair of first connection portions and the other of the pair ofsecond connection portions, and when viewed in the direction orthogonalto the first and second axes, the fifth linear portion extends in adirection inclined with respect to the first and second axes, the sixthlinear portion extends symmetrically to the fifth linear portion withrespect to the first axis, the seventh linear portion extendssymmetrically to the fifth linear portion with respect to the secondaxis, and the eighth linear portion extends symmetrically to the sixthlinear portion with respect to the second axis.
 5. The actuator deviceaccording to claim 1, further comprising: a magnetic field generatorthat generates a magnetic field to act on the coil, wherein the coil hasa spiral shape and surrounds the first movable part when viewed in thedirection orthogonal to the first and second axes.
 6. The actuatordevice according to claim 1, wherein the coil is arranged at a positioncloser to the outer edge than the inner edge of each of the pair ofsecond connection portions on the second axis when viewed in thedirection orthogonal to the first and second axes.
 7. The actuatordevice according to claim 1, wherein the coil includes a portionextending in a direction orthogonal to the magnetic field.
 8. Theactuator device according to claim 1, wherein the coil is made of ametal material of which the density is higher than the density of amaterial of the second movable part, and is embedded in the secondmovable part.
 9. The actuator device according to claim 1, wherein eachof the pair of second connecting parts extends meanderingly when viewedin the direction orthogonal to the first and second axes.
 10. Theactuator device according to claim 1, wherein the second movable partfurther includes a pair of third connection portions, and one of thepair of third connection portions is connected to one of the pair of thefirst connection portions and one of the pair of the second connectionportions and the other of the pair of third connection portions isconnected to the other of the pair of the first connection portions andthe other of the pair of the second connection portions.
 11. Theactuator device according to claim 10, wherein when viewed in thedirection orthogonal to the first and second axes, each of the pair ofthe third connection portions extends in a direction inclined withrespect to the first and second axes.
 12. The actuator device accordingto claim 1, wherein the width of each of the pair of the secondconnection portions is larger than a width of each of the pair of thethird connection portions.
 13. The actuator device according to claim 1,wherein the second movable part has a shape elongated in the first axisdirection when viewed in the direction orthogonal to the first andsecond axes.
 14. The actuator device according to claim 1, wherein awidth of an end portion of each of the pair of first connecting parts ona side of one of the pair of first connection portions increases asapproaching the one of the pair of first connection portions when viewedin the direction orthogonal to the first and second axes.
 15. Theactuator device according to claim 1, wherein a width of an end portionof each of the pair of first connecting parts on a side of the firstmovable part increases as approaching the first movable part when viewedin the direction orthogonal to the first and second axes.
 16. Theactuator device according to claim 1, wherein the first movable partincludes a body portion, a ring shape portion, and a pair of connectingportions, and when viewed in the direction orthogonal to the first andsecond axes, the ring shape portion is formed to surround the bodyportion with a gap therebetween and the body portion and the ring shapeportion is connected to each other by the pair of connecting portions.17. The actuator device according to claim 16, wherein the pair ofconnecting portions are connected to the body portion on both sides inthe second axis direction.